Synthesis and characterization of Na2Ti6O13 and Na2Ti6O13/Na2Ti3O7 sodium titanates with nanorod-like structure as negative electrode materials for sodium-ion batteries

• DOI: 10.1016/j.est.2017.07.008
• Publication Date: 2017-11-10T09:17:12Z
• Authors: Ondrej Cech; Klara Castkova; Ladislav Chladil; Premysl Dohnal; Pavel Cudek; Jiri Libich; Petr Vanysek
• Keywords: Monoclinic crystal system; Nanorod; Nanometre; Hydrothermal Synthesis

Abstract In this work, we report microwave assisted hydrothermal synthesis of monoclinic sodium titanates with either tunnel or with mixed tunnel/layered structure. Single phase Na2Ti6O13 and mixed phase Na2Ti6O13/Na2Ti3O7 titanates were studied by electrochemical measurements with cyclic voltammetry, impedance spectroscopy and galvanostatic cycling. SEM images revealed that all the synthesized materials consist of rods with widths in the range of tenths to hundreds nanometers. XRD analysis was used for determination of the phase composition and crystallite size. It was shown that mixed phase electrode material reveals higher capacity and wider active voltage range but has also lower cycling stability. The insertion potential of layered titanate Na2Ti3O7 is much lower than in the case of Na2Ti6O9 and the specific capacity of mixed titanate in the first cycle is double the capacity of pure Na2Ti6O9. Although presence of layered titanate contributed to high specific capacity in early cycling, it allowed a considerable decrease in specific capacity at higher numbers of cycles.